1. Technical Field
The invention relates generally to fifth wheel assemblies for coupling semi-trailers to tractors. More particularly, the invention relates to a carrier assembly which is mounted on the vehicle frame for movably supporting the fifth wheel supporting carriage. Even more particularly, the invention relates to such a carrier assembly which is adjustable for various width tractor frames and which facilitates positioning and replacement of the carriage on the trailer.
2. Background Information
Large highway freight trailers are usually coupled to a tractor by a fifth wheel assembly may include a top plate and a side bracket or carriage assembly having a locking device which engages the slide bracket in a selected position. The fifth wheel top plate is mounted on the carriage assembly which is movably adjustably mounted on a carrier assembly which is secured to the tractor frame.
These slide plates or carrier assemblies are usually custom made to fit a particular type of tractor due to the size of the tractor frame. For certain applications it is necessary to adjust the position of the carriage assembly on the carrier assembly in order for the locking mechanism to be compatible with the location of the trailer king pin to provide a desired weight distribution on the rear suspension of the tractor. Likewise, this position affects the turning radius that can be achieved between the tractor and trailer. This adjustment of the carrier and carriage assemblies with respect to each other and to the tractor frame is relatively complicated and expensive due to the welding and unwelding of various parts.
Carrier assemblies have various stop plates welded across the ends of the carrier to limit the position of the carriage assembly to prevent excessive movement of the carriage on the carrier assembly resulting in a dangerous turning radius and undesirable weight distribution on the tractor rear wheels. Heretofore, these stop members were welded into position and required breaking of the weld and rewelding the stop plate in a newly desired position, especially when replacing the slide plate assembly for maintenance or adaptability for use with a different trailer.
Another problem with existing fifth wheel assemblies and in particular the carrier assembly therefor, is that the racks along which the carriage assembly is movably mounted and subsequently positioned by a pair of opposed plungers or other retention mechanism, are usually single linear lengths of a rack which require replacement of the entire rack should one of the teeth become damaged. This is an expensive procedure requiring numerous welds to be broken in order to remove the rack and then rewelded along the entire length once the new rack is put in place. Likewise, the cost of the new rack is expensive for replacing only one or several broken teeth.
Still another problem with existing carrier assemblies is the unequal weight distribution of the carriage and slide plate on the carrier assembly resulting in increased maintenance problems.
Another problem with existing fifth wheel assemblies is that the spring biased plungers which secure a carriage assembly in a fixed position on a carrier assembly, may require replacement in order to match a particular width trailer frame. This is expensive and undesirable. Furthermore, over time, the biasing force of the plunger biasing springs will weaken due to wear, temperature and the harsh environment in which they are located, which could cause premature release of the plungers from the carrier rails.
Thus, the need exists for an improved carrier assembly for movably supporting a carriage assembly thereon of a tractor fifth wheel to eliminate problems with prior art carrier assemblies.
The present invention provides a carrier assembly for movably supporting a fifth wheel assembly of a tractor trailer combination which is readily adjustably mounted on the spaced frame members of a tractor by a plurality of bolts along the length of the frame mounting angle.
Another aspect of the invention provides a carrier assembly having adjustable stop members at opposed ends of the carrier which can be slidably adjusted easily along the length of the carrier in order to properly position the carriage assembly thereon, and which can be easily removed to permit replacement of the carriage and the slide plate assemblies.
Still another feature of the invention is the forming of the carrier assembly slide rails as integral one piece members having a U-shaped portion on which the rack is welded whereby each of the slide rails is easily mounted on the tractor frame member and is able to receive and distribute the weight of the carrier in a more efficient and effective manner.
A further aspect of the invention is forming the racks on the slide rails of a plurality of rack segments, each segment being secured to the slide rail by a pair of welds, whereby only a single segment need by replaced should one or more of the teeth be damaged avoiding the heretofore required replacement of the entire rack.
A feature of the improved carrier assembly is the adjustability of the mounting brackets for the stop members enabling them to be mounted on tractor frame members of various spacings replacing the heretofore single piece stop members that are welded on the space frame members.
Another aspect of the invention is providing locking plungers for securing the carriage assembly in a fixed position on the carrier assembly which are adjustable in length to compensate for different width trailer frames and to ensure a constant spring tensioning force for maintaining the plunger teeth in engagement with the teeth on the carrier assembly rails to prevent premature release.
The foregoing advantages, construction and operation of the present invention will become more readily apparent from the following description and accompanying drawings.